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Furnace venting

I have a house that there are 3 - 5" metal vents coming out the side of the house. The middle one is exhausting heat from the furnace. The other 2 I do not know what they are for (bringing air into the furnace??) There are no covers on these vents. They are located under a deck the underside of which was covered and I had pulled over the cover and its the first time I had seen these.
I am worried about bugs..etc getting into house because the metal comes to edge of the house siding but there are small gaps.
Should I cover holes with some type of vent like those used for dryers?

Re: Furnace venting

You would need to find out what's connected to these vents and where they go before deciding on which type of hood .

If the gaps are between the siding and the metal duct then you could fill those gaps with caulk or canned spray foam to seal.

Gray Watson
Re: Furnace venting

As mentioned you'd need to know what the vents are for before you considered a hood, louvers or dampers. You may already have an internal damper system for a fresh air intake or heat recovery ventilator.

Instead of filling a void with spray foam or caulk, I'd recommend using a duct seal compound as the first packing product between the flashing plate and the siding, which you can buy in one-pound blocks for less than two dollars at any home store or hardware store. It will deter insects and vermin unlike spray foam and won't shrink or stress crack like caulk will. You can paint or caulk overtop if you'd like. Duct seal compound is designed to be exposed up to 180 degrees F and extreme sub zero temperature exposures.



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